Treating subdivided solids



United 2,711,387 TREATnvG sUBDIviDEDsoLiDs George L. Matheson, Union, and Homer J. Hall, Cranford, N. J., assigiiors to Esso Research and Engineering Company, a corporation of Delaware Application November 30,1949, Serial No. 130,216 i 6 Claims. (Cl. 20214) The Present invention relates to the treatmentofsubdivided solids. to a method of contacting subdivided solids with uptlow.v

thecarbonization or`r gasiication of coal. Waste coal obtained inthef course of conventional coal mining processesis composedof particles varyingin size from a few More particularly, the invention pertainskr Y ing gases at gas iiow velocities adapted Vto rmaintain the subdivided solids in the form of a highly turbulent ebullient mass resembling a boiling liquid. In its more specific aspects, the invention is directed to the Afluidization, of relatively coarse solidfparticles, having particlesizes of about 500 microns. and more in such Aa manner thatl stratification or the formation of gas slugs in the tiuidized mass and resulting iluidization troublesare avoided.

Prior to the present invention subdivided solids have been contacted with gases in a quasi-liquid or iluidized,

state by passing the gases upwardly through," anduniformly distributed over the cross-sectionalarea of, acon tacting zone containing a body of the subdivided .solids.f This quasi-liquid tiuidized state involves arapidicirculaf. tion of the subdivided solids in `all conceivabledirections:

throughout the fluidized bed.

Numerous important advantages result from this type4 of lluidized solids handling. The contact between gases and solids, as well as between individual solid particlesis formation.'

microns torasmuch astive or more millimeters, the particlels'ize distributionrbe'ing substantially continuous over the entire range, i., e., particlesall. intermediate sizes beingpresent. Similar conditions prevail for othermin-4 erals such as .limestone-.various ores, etc. whichirequire treatment with gasesjforburning/.roastingv reducing or steam refining treatments. Attempts of carryingout suchk Jgas. .treatments in the fluidizedf'state 'have frequently en y' countered serious difficulties as the result of excessiveslug? They present invention avoids these difli# cuties.; t

The present invention isf based on .thesurprising dis? coveryf that slug formationlinuidizedbedscontaining. s substantial proportions- 1 ofi particles `,largerf than (500` microns and particles within,fthegrangeV of *-500 microns isV a direct result offa, con tinuo'us particlesize distribution,

i. e. Vthe V`presence. of particles ofall size ,ranges intermediate .between the .smallest and largest component particles. Ithas been found that no .slugs are formed4 land uniform,fluidizationmay be maintained when a major considerably improved as compared with'othertypesof gas solids contacting such as fixed .or moving bed or operating with a true dispersed suspension. Also, substantially uniform temperature may be maintained throughout a iluidized bed of solids because ofthe rapidcirculationi I and high turbulence of the solids within the rbed, which.

result in au extremely efficient transfer of heat from`V particle to particle and between dilerent sections of the f bed. For the same reasons heat may be added to, Yor extracted from, a uidized solids bed with the greatest of ease and uniformity. a

Fluid operation has been. successfully employedY inv many chemical catalytic and non-catayltic processes, as'

150 are certain inherent limitations in this techniquewhich,` have limited its eiciency in somer of the eldsforwhich well as physical separation processes. However, there it has offered substantial promise. Y L

One of these limitations results from encountered in the luidization of subdivided solids Vcontaining substantial proportions of coarse particles of .more than, say, 500 microns size. When it 'is attempted to iuidize solids of this type in reactors having a ratio -of height to diameter of, say,A about 2 or more, `gas slugs are formed, i. e. large bubblesof substantially Vsolid-free iluidizing gas, which pass upwardly through the reaction:

` about 15,0 microns,.

together, giving Y'riseto' than vr10% of the line fraction proportion ,o f'the particles are within thelowest size bracket, for example fromabout 0- 200 microns, or Vfrom l l 1 0- 150 micxjons,y and a minorV proportion ofthe particles `are-larger thanabout`-500 `microns size, to the substantial exclusionof all'l intermediate particle sizes. The"` linear Vsuperficial tlow `velocity of the iiuidizing gasmust be sulicientV foran incipient tluidizationl of the Vcoarsest com- Y ponent particlesin .the absence of tine particles. It has Y further. beenlfound thatltliisslu`gifree particle sizedistially more than about V35% by volume of said coarsepar-Y ticlesfv I f this V,limit ,is exceeded,the coarse-particles lock poor liuidization. Theremainder o fjthe'fbed rsholuldrcon'sist of A larger than about 200 micro s. f Specifically, not more tion should be inthe 200-,500-. micron range. YThe ratio ofthe minimunidiameter of the coars e particles to the y maximum diameter of thene particles should beat least.`

ZVzfLjand is preferably knot less than 4:1; ranges are about 104 30% `by volume of the coarse particles having ,sizesl larger than.k about 600-microns and 70-90%` byvolume of particles having sizes smaller than with substantially noY particles present V in the 1 50.600 micron-range. As previouslyV stated, thesuperficial linearvelocityv-rof the Preferred general, it may be stated, however, thatvsupercial linear `gas YQlQoities of about 1.0-3' ft. persecond are; adequate properlvptotiuidize .such'solids kas coal, coke, yshale,'vai' chamber and disrupt the uniformity of -the solids distribution throughout the reaction zone.` 1 v The importance of this problem becomes apparent; from the fact that the solidscharged to numerous gas.-k solids contacting processes, to which the tluid solids technique as such is very well suited, are krecovereclfrom, natural deposits or from processes of preparationginfthe form of masses of subdivided solids containing substane-`` tiel. angesagter-*afirmarse:particles-ialanmvithftreadilvn?? angenehme-miamusica; @straining sohvaifpercenier'm lliaahlapattislss sattlaaiae ianssaataeaniewaeaea straal kmicrons 'particle size and 20 vol. percent of microns. An outstanding example for such processes is` from 0 to about 850'microns.

iouso'res vand thelike, although4 higher velocities may be employed inthe treatment of very coarse or dense solids.

The following example will further illustrate the presentinventiomn t Example A silica-aluminaV gel catalyst, vcontainingrrabout vl2%- by.weighi of aluminaand having a specifictgravity of about 1:0; wasl ground tovarious `From' this material two blends ywere .prepared as follows: a) la blendjinxa'ccordsassi-gg fiiwagmsiiimnagiisaaadefies material yon `particles not 'substantiallyf or 10% of the coarse fracfluidizing gas depends Asomewhat onthe true specific gravity of the solids.

particle l,sizes varying anatra Mesh Vor Both blends were tested in a 1 inch inner diameter glass column at a settled bed depth of the solids of lit., using" air as the fiuidizing gas at a superficial linear velocity 1.25 ft. per second. At these conditions blend (tlwas uniformly Viluidized without any slug formation, while blend (b) slugged badly. K

It will be appreciated that the present invention affords a suitable means for the slug-free iluidizatio'r'i of subdivided solid masses containing coarse particles of more than 500 microns size in all concentrations. It merely necessary to eliminate particles of intermediate size, say from Z200-50() microns, from such mixtures and to adjust the concentration of particles of less than 200 microns, preferably 150 microns, to' above about 65 vol. percent. In cases in which the solids to be treated consist predominantly or exclusively of coarser particles, the solids charge may be supplied continuously to a treating vessel containing a large excess of a solids mass consisting- Y of particles of smallest size. This excess may be maintained by continuously withdrawing a portion of the fluidized mass, blowing nes from said portionba'ck into' ythe iluidized mass and recovering substantially exclusively coarse particles from said portion. Y n

A system particularly adapted for carrying out the last named embodiment of the invention is diagrammaticlly illustrated in the single figure of the annexed drawing. The operation of the system will be forthwith explained using the carbonization of coal as an example. It should be understood, however, that the system may be applied in an analogous manner to the treatment of other s'ubdivided solids inthe iluidized state.

Referring now to the drawing, the numeral 10 designates a uid type reactor provided in its lower portion" with a gas distributing means such as grid 12. Reactor 10 isv connected with a solids withdrawal and elutriation well 15 which, in its lower portion, is likewise provided with a grid 17. Gas-solids separation means such as one or more cyclones 20 may be arranged in the top of re'- actor 10. Y l

In operation, reactor It) may be supplied with coke having a particle size of minus 200 microns, say of about 15.0- microns. Sufficient coke of this particle siz'ey is placed into reactor 11i so that a uidizedhighly turbulent coke bed having a more or less well defined upper l level L10 at a point abovel the inlet into Withdrawal well 1.5 is formed when a gas is admitted through grid 12 at a sup Y cial linear velocity of about l-l.5 ft.vper second. The coke charge may then be luidized and brought up toma carbonization temperature of about 800-900 F by admitting superheated steam of about l0()0121()0"y E. through line 1 and grid l2 into reactor 10 at the velcci'ty` specified above. Simultaneously, fresh run=ofr`nine slack coal consisting of about 95 vol. percent of particles of 500 microns or more and only about vol. percent'do 0l50 micron particles is supplied through lineS. The tine and coarse fractions can be introduced in any suitable manner, for example through line 3 or through iluidizing gas inlet 1, or a portion through each. The coarse. material tloats in the liuidized coke mass with the, eiect that it partakes in the extreme turbulence of the uidized bed and in all other benefits of the uidized state.

A portion o f theV tluidized mass flows from reactor into well wherein it is aerated by a second stream of superheated steam supplied via line 5 and grid 17. An-

amount of treated solids adequate to maintain the desired particles to settle down while coke nes remain iluidized in well r15 or are returned from well 15 to reactor 10. The permanent presence of a large excess of coke fines has the additional advantagerof preventing the fresh coal fed from agglomerating due to its passage through a plastic state in the course of being heated to carbonization temperature. u v

The gas velocity in well "15 may Valso be readily so controlled that all desirable stages between complete separation of coarse material and fines and uniform fluidization of coarse material and fines may be accomplished. In this manner, the Vsolids withdrawn from the bottom of well 15 through line 22 may either be coarse material alone or any desired mixture of coarse and iine material whereby a proper control of the particle size distribution within reactor 10 may be accomplished. Depending-on the elutriative` etect desired, the supercial linear gas velocityin well 15 may vary within the approximate range of 0.34.5 ft. per second in the case of the present example.

A mixture of steam and volatile carbonization products passes upwardly from level L10 and is withdrawn through line ZS'preferably after separation of entrained solids in cyclone 20. Solids separated in cyclone may be returned via line 21 to the fluidized bed in reactor 10. Alternately, the cyclone may be located outside of the shell of reactor 10 and the separated lines can be returned to the bed via line 3 or line 1.

The operation of the system of the drawing may be modified? invarious respects. Heat may be supplied to reactor 10 by internal or external heating means, such a's heating coils or a heating ljacket or by partial combustion supported within the fluid bed by admitting a' free oxygencontaining gas through line 1 and grid 12 or by the circulation of hot heat-carrying solids between reactor l0 and separate solids heater, all in a manner known per se. Other gases, such as nitrogen, ue gases, product gas from the carbonization process, etc. may take the place of steam as the fluidizing gas and/or heat carrier. Water gasmay bel produced in reactor 10 in an analogous manner by supplying steam through grid 12 and raising the temperature' above about 1700" F. The burning of lime and the roasting or reduction Vof ores and various other solids treatments may be carried out in reactor 10 in amanner largely analogous to that described above.

Other modifications will appear to those skilled in the gasifortn material to form a highly turbulent dense of solids resembling a boiling liquid and maintained inl a uidized condition by upwardly owing gasiform mafterial without' stratification of coarse particles in said r'na'ss'4 and having a ratio of height to diameter Yof not less' than 2A andA containing comportent solid particles having'wA particle size coarse enough to cause slug formation ina ililidized ni'ass' where the' particle size Arange extends throughl the entire yrange, from' o te 50u mierdas and larger, the improvement which comprises maintaining in a contacting ione having a ratio of height to diameter of more than 2, a' dense fluidiz'edmass of solids consisting essentially of a 'major proportion of tine solidparticles oiless than 200 micron size and a minor proportion of coarse-'solid particles of at least 500 micron size, feeding subdivided solids consisting essentially of vcoarse solid particles of at least 500 micron size and finely divided` Y iluidization of said coarse solid particles of at leastrStlQ micron size in the absenceof said finelyk divided particles of less than 200 micron size, and ywithdrawing ak mixture of solids containing coarse particles and inely divided particles from said'dense turbulent uidized mass.

in said contacting zone. Y

2. A method according to claim l wherein thersolid's in said dense fluidized mass comprise coke. i

3. In a method of contacting subdivided solids with ya gasiform material to forma highly turbulentrdense mass resembling a boiling liquid'maintained in a fluidized condition by upwardly flowing gasiform material without stratification of coarse particles in saidmass and containing component solid particles having a particle size coarse enough to cause slug formationin a uidized'mass having a ratio of height to diameter more y,than 2 where the particle size range extends from 0 to 500 microns and a'` i `r substantial proportion of particles larger than 500 microns, the improvement which comprises maintaining in a contacting zone having a ratio of height to diameter of more than 2, a dense turbulent iluidized mass of solids consisting essentially of about 70 to 90%' by volume of tine solid particles of less than about 200 micron size and about 10 to 30% by volume of coarse solid particles of at least 500 micron size, with substantial exclusionlof particles in the range of 200 to 500 microns, feeding subdivided solids consisting essentially of coarse solidfparticles of at least about 500 micron size and finely divided solids of less than about 200 micron size to said dense extremely turbulent uidized mass, adjusting the linear superficial ow 'velocity of said gasiform material to aV value suicient for an incipient luidization of said coarse solid particles of at least 500 micron size in the absence of said nely divided particles of less than 200.micron j 5. In a method of contacting subdivided solids with Y gasiform material to form a highly turbulent mass resembling a boilingrliquid maintained in a dense fluidized condition by upwardly flowing gasiform material with out stratification of coarse particles in said mass and containing component solid particles having a `particlesize coarse enough to cause slug formation in a uidized size, withdrawing from said contacting zone a mixture ofvfsubdividred Vsolids 'containingqcoarse' solid lparticles Y of at leas'tiaboutSOUmicron size and .iinej'solidY particles` of lessk Vthan'about200 micron size from Vsaid kdense 1 fluidized mass into a -vsolids fractionating zone, separating in saidfractionating zone coarse solid/particles offat-. f V n least about 500 niicron size from l*fine solidparticles'havingwless than Yabout 200r micron- `size, withdrawing' said j separated coarsesolid particles from said fractionatingVv ff zone, returning said separated fine solid particles having', 'y

less than aboutlOO microny size to v,said dense fluidized 1 turbulentimassfand controlling the rates fof coarsekangl l. j ne solids feed andwithdrawal4 tofand from said' dense uidized turbulent mass in Vsuch `arnarrnerfjtliat@the` con- Y centration of coarse'srolid particles of atleast about'SOOg, f micron size in all portions of-saidfuidizedturbulent-mass l V f is `from'about 10to 30`%`by volumeand'the,-concentrall tion of tine particles 'below about1`2'00micron;sizejinfk 1. all portionsof saidmdens'e uidized turbulentrrlassf.isfV i' 'I 20V Y from aboutY 70 to. 90:9 bfby volume-'y j z ythroughout theranga -fromfpowder 'to coar'sefparticl'es `above about l500 microns,` the improvement which 'comprises maintaining the particle 'size distribution infsaidv Y ldenseifluidized extremely turbulentmassl having a ratioY of -height todiameter of` more than 2 such thatthe' coarsev Lsolid particlesiof aj size larger thanabouitzHSiOO microns yforrn'aliout l0-30% by'volume of said.,densewiluidizedsm extremely turbulent mass and'the'ne'solid'particlesl.; smaller than about 200microns formY about l70'-`9:0%

by volume kof said` densel tiuidized extremely turbulent mass', saidv dense" uidizedturbulent mass containing su stantially. noiparticles in the particlesize-tran'geoff about 2.00 to 500 microns.

mass having a ratio of height to diameter of more than 2 wherein the particle size extends throughout the range from powder to coarse particles above 500 microns,ithe improvement which comprises maintaining in a contacting zone having a ratio of height to diameter of more than 2, a dense fluidized turbulent mass ofsolids Y icial flow velocity of said gasiform material to a valve4 sufficient for incipient fluidization of said rcoarse solid particles of at least about 500 micron size in the absence of said fine solid particlesof Vless than about 200 micron References Cited in the tile'ofithispatentY1 UNITED STATES PATENTS Engineering Progress, vol. 43, No.;8, August 1947, pp. V429-436. i i

Y 6. In a method yofcontactingjsubdividedsolids with,L "a gasiform"materialinfaffcontactingzone-to'forma highly turbulent*dense.massi,'resemblingfaboilingfliquidl, i Yand maintained' in a densefuidiz'ed conditiorr'byQup-ff' wardly flowing gasiform'materialiwithout stratificationi` of coarse particles lin .said dense 'uidizedhighlyturbu-.ly Y Ylent mass having a ratio of `heightto Y diameterA of more Y 1 than Ziand containing componentl solid?particles-'having a particle .size coarse enough to cause -slug'for'mation l' i f inV afiluidzed massl whereff'the particlewsize extends -f 

1. IN A METHOD OF CONTACTING SUBDIVIDED SOLIDS WITH A GASIFORM MATERIAL TO FORM A HIGHLY TURBULENT DENSE MASS OF SOLIDS RESEMBLING A BOILING LIQUID AND MAINTAINED IN A FLUIDIZED CONDITION BY UPWARDLY FLOWING GASIFORM MATERIAL WITHOUT STRATIFICATION OF COARSE PARTICLES IN SAID MASS AND HAVING A RATIO OF HEIGHT TO DIAMETER OF NOT LESS THAN 2 AND CONTAINING COMPONENT SOLID PARTICLES HAVING A PARTICLE SIZE COARSE ENOUGH TO CAUSE SLUG FORMATION IN A FLUIDIZED MASS WHERE THE PARTICLE SIZE RANGE EXTENDS THROUGH THE ENTIRE RANGE FROM 0 TO 500 MICRONS AND LARGER, THE IMPROVEMENT WHICH COMPRISES MAINTAINING IN A CONTACTING ZONE HAVING A RATIO OF HEIGHT TO DIAMETER OF MORE THAN 2, A DENSE FLUIDIZED MASS OF SOLIDS CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF FINE SOLID PARTICLES OF LESS THAN 200 MICRON SIZE AND A MINOR PROPORTION OF COARSE SOLID PARTICLES OF AT LEAST 500 MICRON SIZE, FEEDING SUBDIVIDED SOLIDS CONSISTING ESSENTIALLY OF COARSE SOLID PARTICLES OF AT LEAST 200 MICRON SIZE AND FINELY DIVIDED SOLIDS OF LESS THAN 200 MICRON SIZE TO SAID DENSE FLUIDIZED MASS, ADJUSTING THE LINEAR SUPERIFICIAL FLOW VELOCITY OF SAID GASIFORM MATERIAL TO A VALUE SUFFICIENT FOR AN INCIPIENT FLUIDIZATION OF SAID COARSE SOLID PARTICLES OF AT LEAST 500 MICRON SIZE IN THE ABSENCE OF SAID FINELY DIVIDED PARTICLES OF LESS THAN 200 MICRON SIZE, AND WITHDRAWING A MIXTURE OF SOLIDS CONTAINING COARSE PARTICLES AND FINELY DIVIDED PARTICLES FROM SAID DENSE TURBULENT FLUIDIZED MASS IN SAID CONTACTING ZONE. 